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Novel blood test predicts ICD need in heart failure

A novel blood test can predict sudden death risk in heart failure patients, and could help to determine whether patients need a defibrillator implanted, according to a study1 presented recently at the ESC Congress 2012, held in Munich, Germany.

The clinical trial showed that a blood test can predict which patients will need an implantable cardioverter defibrillator (ICD) in the next year. The test identifies changes in the gene message (mRNA) for the SCN5A gene – an increase in the changed gene message was able to predict who would have a sudden death episode requiring defibrillation.

Professor Samuel Dudley (University of Illinois at Chicago, US) and his team evaluated the new blood test in 180 adult patients, including 135 patients with heart failure and 45 patients without heart failure as controls. Patients with congenital heart disease, infections, and inflammatory conditions were excluded.

The SCN5A gene was measured in heart muscle cells and white blood cells. The changes in the gene message were able to predict who would have a sudden death episode requiring defibrillation. Heart failure patients who had abnormal heartbeats that would normally cause sudden death had significantly higher levels of these gene variants compared to patients who did not have abnormal heartbeats. The amount of variants in the blood had excellent predictive power to determine arrhythmic risk, suggesting that a blood test for sudden death risk and the need for an ICD is possible.

Figure 1. Distribution of test values in controls (black), patients with HF and no ICD shocks (i.e. no sudden death episodes; blue), and patients with HF and an ICD shock (i.e. an aborted sudden death episode; red).

Figure 1 shows the distributions of the C type SCN5A variant (VC) in controls, patients with heart failure (HF) and no sudden death (i.e. no ICD shocks), and patients with HF and a sudden death episode (i.e. with ICD shocks). The separation of the distributions of patients with and without a sudden death episode allows for a discriminatory test.

Figure 2 is a receiver operating characteristic (ROC) curve which shows that the discriminatory power of the C or D type variants of SCN5A as measured by the area under the curve are equivalent and much higher than an ejection fraction of less than or equal to 20%.

“This is the first test of its kind,” said Professor Dudley. “It is amazing stuff, with promise to change dramatically the way we direct treatments to patients at risk for sudden death”. The next steps in the development of the test will be to carry out a larger trial and work with regulatory agencies to receive approval for clinical use, Professor Dudley added.

Figure 2. ROC curve for the PulsePredic assay generated to evaluate the performance of the variants and ejection fraction (EF) ≤ 20% in distinguishing the need for an ICD. Area under the curve (95% CI): Variant C (blue) = 0.98 (0.95, 1.00), Variant D (green) = 0.97 (0.93, 1.00), EF ≤ 20% (gold) = 0.61 (0.41, 0.71). The purple line is the line of no discrimination or a test with no discrimination power.